1. Field of the Invention
The present invention generally relates to etching methods.
2. Description of the Related Art
A method for forming holes of a high aspect ratio in a silicon oxide film by etching in a low temperature environment has been proposed. (See, for example, Japanese Laid-Open Patent Application No. 7-22393.) For example, in manufacturing three-dimensional stacked semiconductor memories such as 3D NAND flash memories, it is possible to form holes or grooves of a high aspect ratio in a laminated film of silicon oxide films and silicon nitride films and in a single-layer silicon oxide film by etching using the above-described method. For related art, reference may also be made to Japanese Examined Patent Publication No. 62-50978, Japanese Examined Patent Publication No. 7-22149, and Japanese Patent No. 2956524.